In recent years, an electric compressor driven by a motor has been developed to be used in an air conditioner of a vehicle such as an electric vehicle, a hybrid vehicle, and a fuel cell vehicle. Rotation speed of the motor is generally controlled by a motor driving circuit unit using a semiconductor switching element. The semiconductor element has a large heating value, so that it is required to appropriately dissipate heat. Thus, a variety of proposals like the following have been provided.
Patent Literature 1 describes an electric compressor for an air conditioner of a vehicle, in which an axis of a motor and a compression mechanism is set horizontally. The electric compressor includes a housing having an upper surface with which a box-like inverter housing section is integrated. The box-like inverter housing section is provided in its bottom face with block-like heat sinks divided in accordance with arrangement of semiconductor elements. When a metal plate integrated with a circuit board provided with the semiconductor elements is arranged horizontally on a boss provided in the bottom face of the inverter housing section to be fixed thereto, the semiconductor elements are brought into contact with the respective heat sinks. Accordingly, heat generated by the semiconductor elements is dissipated into a refrigerant at a low temperature to be sucked into the housing through the heat sinks. Since there are the divided heat sinks, each of the semiconductor elements is uniformly cooled.
Patent Literature 2 also describes an electric compressor in which heat of a semiconductor element is dissipated into a refrigerant to be sucked into a housing. In Patent Literature 2, a circuit board is arranged so as to be perpendicular to an axis of a motor and a compression mechanism that is set horizontally, and one side of the circuit board is brought into close contact with a wall of the housing. In addition, the housing that houses the circuit board is provided with an intake port and an exhaust port for ventilation of inside air and outside air, so that warmed air inside the housing is discharged through the exhaust port to prevent heat accumulation inside the housing.
Further, in Patent Literature 2, a thermo-module facing the other side of the circuit board is provided as an auxiliary cooling device. The thermo-module includes a Peltier element and a radiating fin, and heat absorbed in the Peltier element by energization of the Peltier element is dissipated to the outside of the housing through the radiating fin.